Twitter upgrade tears down service

Twitter warned users that a failed upgrade Monday night has left the site unusable for many.

The problem began past 8 p.m. PDT, the company said, and might last for hours. "Our infrastructure and operations engineers are currently working to resolve this. The site could be down until approximately 3 a.m. PDT," company spokeswoman Carolyn Penner said. The Twitter status page blamed the problem on "the failed enhancement of a new approach to timeline caching."

Signs of problems included the infamous "failwhale" image indicating problems, another image signifying "Something is technically wrong," missing or late tweets, duplicate tweets, and a Web page that didn't work at times.

For more on this story, read Twitter whacked by hours-long problems on CNET News.